1. Field of the Invention
The invention relates to automatic swimming pool cover systems, and in particular, to hydraulic drive systems which rotate the cable reels and cover drum for extending and retracting pool covers back an forth across a swimming pool.
2. Description of the Prior Art
Automatic swimming pool cover systems typically include a flexible vinyl fabric sized so that most of it floats on the surface of the pool water. The pool water acts as a low friction surface significantly reducing the amount of force required to move the cover across the pool. The front edge of the cover is secured to a rigid boom spanning the width of the pool for holding the front edge of the cover above the water as it is drawn back and forth across the pool.
To draw the cover across the pool, a cable, typically a Dacron line, is incorporated into and forms a beaded tape which is sewn or attached to the side edges of the pool cover. The beaded tape in turn is captured and slides within a "C" channel of an extruded aluminum track. The track is secured either to the pool deck or to the underside of an overhanging coping along the sides of the swimming pool. The cables extending from the beaded tape sections of the cover are trained around pulleys at the distal ends of the tracks and return in a parallel "C" channel to the drive mechanism where they wind around cable take-up reels.
To uncover the pool, the drive mechanism rotates a cover drum mounted at one end of the pool winding the pool cover around its periphery and unwinding the cables from around the take-up reels. To cover the pool the drive mechanism rotatably drives the cable take-up reels winding up the cables to pull the cover across the pool unwinding the cover from around the cover drum.
In related application Ser. No. 07/913,796 filed Jul. 16, 1992 and in U.S. Pat. No. 5,184,357 issued Feb. 9, 1993, the applicant describes automatic swimming pool cover systems wherein a first hydraulic drive provides torque for resisting cover drum rotation during cover extension and for rotating the cover drum for cover retraction, while a separate second hydraulic drive provides torque for rotating the cable reels for cover extension and for resisting cable reel rotation during cover retraction. In the related application and patent, the applicant teaches the desirability of having positive stops located at the respective ends of the pool for stopping movement of the rigid leading edge carrying pool cover by increasing tension load on the cover and cables sufficiently for counter-balancing the torque of the particular driving hydraulic motor rotating either the cable reels or cover drum. He points out that such stops need only be able to mechanically withstand the differential load of the driving hydraulic motor rotating the cable reels or cover drum and the opposing tension load imposed by the pumping hydraulic motor resisting rotation of the cover drum or cable reels. In systems utilizing a single reversible hydraulic motor such stops must be able to mechanically withstand the load imposed by the driving hydraulic motor which is typically determined by a pressure relief valve mechanism in located in driving side of the hydraulic liquid ciculation loop.
In under track systems (where the track is fastened to the underside of overhanging copings), the copings or walls at the respective ends of the pool can function as inherent stops arresting cover extension or retraction provided the rigid leading edge appropriately engages the coping or walls. Also, return pulleys at the distal ends of the respective tracks returning the cables to the take-up reels provide inherent positive stops for arresting extension of the cover in that the pulley housings do not have "C" channels and hence will stop the sliders sliding within the "C" channels supporting the rigid leading edge carrying the cover across the pool. [See U.S. Pat. No. 4,939,798 issued Jul. 10, 1990 to applicant, Harry J. Last, entitled: "LEADING EDGE AND TRACK SLIDER SYSTEM FOR AN AUTOMATIC SWIMMING POLL COVER" and U.S. Pat. No. 4,466,144 issued Aug. 21, 1984 to Joe H. Lamb entitled: "PULLEY ASSEMBLY FOR SWIMMING POOL COVER"]
However, in top track systems (where the track is secured to the pool deck) and in other pool configurations, using the walls or copings at the ends of the pool to arrest or stop cover extension retraction by engaging the rigid leading edge is neither feasible nor aesthetic. In fact, many pools are specifically designed to conceal the rigid leading edge of a pool cover under a coping, particularly when the cover is fully retracted. And, in systems where the cable reels and cable drum are located on opposites ends of the pool, there aren't any return pulleys at the distal ends of the track to stop the sliders carrying the rigid leading edge. Accordingly, it is sometimes necessary to provide positive stops terminating the respective proximate and distal ends of the "C" tracks securing the beaded tape side edges of a pool cover which establishes the end points of travel for the sliders sliding within the "C" channels of the track carrying the rigid leading edge.
In many existing automatic pool cover systems, at the proximate end of the tracks adjacent the cover drum, there are cover edge guides which guide the beaded tape side edges of the cover unwinding from the cover drum into the "C" channels of the extruded aluminum track on either side of the pool. In some systems, these cover guides also serve to locate the beaded edge of the cover relative to the cover drum as the cover is wound around the cover drum.
A typical cover edge guide is formed from unitary block of material with a guide channel along at least one side defined by a circular bore with a longitudinal gap communicating from the bore to the side of the cover guide. The channel openings on such cover guides are typically flared to preclude any snagging of the beaded tape edges sliding through the guide. The beaded edge is captured in the circular bore of the guide channel with tape and the cover sliding in the longitudinal gap. The width of the longitudinal slot is typically much less than the side opening of the "C" channel of the track anchoring the cover to the sides of the pool so that the beaded edge cannot slip free of the guide channel. Typically, such cover guides also include an alignment tang or bar shaped for insertion into a rectangular space between the respective "C" channels of the track for assuring alignment of the bore and slot channel of the particular guide with the opening of the "C" channel of the tracks. In essence, cover guides have heretofore simply functioned as tailored extensions of the confining " C" channels of the track proximate the cover drum. Such cover guides are preferably composed of softer materials such as Nylon such that the guide wears rather than the beaded tape cover edges sliding through them. [See U.S. Pat. No. 3,979,782 issued Sep. 14, 1976 to Joe H. Lamb, entitled SWIMMING POOL COVER and U.S. Pat. No. 4,939,798 (supra) FIG. 9, re discussion at Col. 16, 1. 58 through Col. 17, 1.23]
Much to the annoyance of repairmen, because such cover guides are typically formed from unitary blocks of material, the entire cabling extending from the beaded tape edge of the cover be must unwound from the cable reel and pulled through the guide whenever a component of the system including a cover guide must be replaced because of wear or failure. After repair, the entire cable must then be re-threaded and pulled through the guide. Among other requirements, this necessitates removing track sliders secured to the cables supporting the rigid leading edge of the cover (See U.S. Pat. No. 4,939,798). Also, because a cable(s) is completely unwound from around a cable reel, the entire system must then be realigned and re-tensioned.
Also existing cover guides even with flared openings [U.S. Pat. No. 3,979,782] do not address the primary cause of snagging and catching as the beaded tape edge of the swimming pool enters the ends of the "C" channel of the swimming pool track proximate the cover. The primary source of a snags or catches is the abrupt increase in cable diameter at the beaded tape edge of the cover and misalignment of the cover with the slot opening of the track or guide. The abrupt edges at the front edges of the beaded tape on the cable typically catch on the edges of the flared opening particularly when the edge of the cover is not aligned for entry into the slot opening of the guide. Also, the fact that distances between sliders carrying the rigid leading edge and beaded edges of the cover can vary due to stretching, repair, and adjustment further complicate such snagging and catching problems. [See Applicant's U.S. Pat. No. 4,939,798, cols. 15 & 16.]